feat(dev): add the dev-seam Effect boundary module (wave 3.5 stage 3, PR 1)

[ScriptedAlchemy]

Summary

First PR of #152 stage 3 (dev seam). No behavior change — foundation only.

• packages/agent-bundle/src/effect/boundary.ts: the package's sole Effect → Promise/sync edge, mirroring packages/rsc-runtime/src/effect/boundary.ts (runPromise/runPromiseExit/runSync/runSyncExit, makeScopedEffectRuntime, interruptWhenAborted, scopedAbortSignal). Error mapping targets the dev seam's typed contracts: interruption → DOMException AbortError; CodedError subclasses, coded-shape errors (EpochStoreError), and the AB diagnostic carrier DiagnosticError rethrow unchanged.
• effect@4.0.0-rc.112 (exact, same pin as the runtime package) added to packages/agent-bundle dependencies. Nothing imports the boundary yet, so no dist entry changes.
• feat(runtime): Effect v4 foundation — vendored source, boundary module, conventions (#wave 3.5 stage 0) #153 boundary-lint coverage extended: lint tests now pin that packages/agent-bundle/src/effect/boundary.ts is the only legal runner home in this package and that ad-hoc runners in dev-seam files are review-fails (the rule itself already matched any src/effect/boundary.ts).
• docs/effect-conventions.md boundary-module row updated.
• Changeset: patch (internal only).

Parity / gates

• New boundary tests + lint-rule tests: green
• pnpm lint (764 files): green
• pnpm typecheck: green

Refs #152.

[changeset-bot]

🦋 Changeset detected

Latest commit: c7eefc4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
agent-bundle	Patch

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[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-01T17:21:58.464514Z	c7eefc4	PR opened

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